Utility locating system with mobile base station

ABSTRACT

Mobile base stations for use with one or more portable utility locators to aid in determining the location of a particular locator during operation and receive information associated with the utility for storage and/or retransmission to other devices or systems are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application Ser. No. 61/859,706, entitled UTILITYLOCATING SYSTEMS WITH MOBILE BASE STATION, filed on Jul. 29, 2013, thecontent of which is incorporated by reference herein in its entirety forall purposes.

FIELD

This disclosure relates generally to devices and systems for identifyinghidden or buried utilities, such as underground water lines, sewerlines, gas lines, power lines, and the like. More particularly, but notexclusively, the disclosure relates to a mobile base station for usewith one or more portable utility locators to aid in determining thelocation of a particular locator during operation and receiveinformation associated with the utility for storage and/orretransmission to other devices or systems.

BACKGROUND

Utility locating systems, which are used to locate hidden or buriedutilities, are well known in the art. A typical utility locating systemincludes a buried utility locator device, which is a device forreceiving electromagnetic emissions, typically magnetic fields, fromcurrents flowing in a utility being located. The utility may be, forexample, a buried pipe, such as a water or sewer line, a buried power ordata cable, or other hidden or buried conductive objects.

The current flowing in the utility may be inherent currents (e.g.,currents flowing in buried power cables), may be induced by radio wavesor other electromagnetic fields, or may be coupled to or induced by adevice known as a buried utility transmitter (also denoted herein as a“transmitter” for brevity). Buried utility transmitters are devices forgenerating one or more output current signals for coupling to theutility. The output current signals may be at one or more frequencies orsums of frequencies, one or more amplitudes, one or more duty cycles orhaving components in certain signal slots, be of one or more waveforms,and/or one or more phases. The phase and/or timing (e.g., slotconfiguration, of/off timing, etc.) may be synchronized to one or morereferences. For example, the current flow may be phase synchronized suchthat a corresponding utility locator has phase or timing information andcan process the received magnetic field signal, using the phase ortiming information, to extract additional information about the hiddenor buried utility.

SUMMARY

This disclosure relates generally to devices and systems for identifyinghidden or buried utilities, such as underground water lines, sewerlines, gas lines, power lines, and the like. More particularly, but notexclusively, the disclosure relates to a mobile base station for usewith one or more portable utility locators to aid in determining thelocation of a particular locator during operation and receiveinformation associated with the utility for storage and/orretransmission to other devices or systems.

For example, in one aspect, the disclosure relates to a mobile basestation for use in a buried utility locator system. The mobile basestation may, for example, include a vehicle, a plurality of antennasdisposed on the vehicle including a GPS antenna, and WLAN antenna, aplurality of receivers coupled to corresponding ones of the plurality ofantennas, a processing element configured to communicate with ones ofthe plurality of receivers, one or more utility locators, one or moreutility locator transmitters. The base station may further include apower supply subsystem for providing electrical power for the processingelements and plurality of receivers.

In another aspect, the disclosure relates to a utility locating system.The utility locating system may, for example, include a mobile basestation. The mobile base station may include a vehicle, a plurality ofantennas disposed on the vehicle including a GPS antenna, and WLANantenna, a plurality of receivers coupled to corresponding ones of theplurality of antennas, a processing element configured to communicatewith ones of the plurality of receivers, one or more utility locators,and one or more utility locator transmitters, and a power supplysubsystem for providing electrical power for the processing elements andplurality of receivers. The system may further include one or moreutility locators configured to communicate with the mobile base station.The system may further include one or more utility locator transmittersconfigured to communicate with the mobile base station.

Various additional aspect, features, and functionality are furtherdescribed below in conjunction with the appended Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present application may be more fully appreciated in connection withthe following detailed description taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is an illustration of one embodiment of a mobile base stationsystem disposed in a truck cap.

FIG. 2 is an illustration of an alternate embodiment of a mobile basestation system disposed in a trailer.

FIG. 3 illustrates details of a mobile base station embodiment in use inan example locating operation where signaling is provided to a utilitylocator to generate enhanced location information.

FIG. 4 illustrates details of a mobile base station embodiment in use inan example locating operation where signaling is provided to a mobilebase station to generate enhanced location information, which may thenbe provided to a utility locator to apply corrections to locallygenerated location information.

FIG. 5 illustrates details of an embodiment of a method for generatingenhanced location information in a utility locator.

FIG. 6 illustrates details of an embodiment of a method for generatingenhanced location information in a mobile base station and providingcorrection information to a utility locator.

FIG. 7 illustrates certain details of an embodiment of a utilitylocator.

FIG. 8 illustrates certain details of an embodiment of a utilitytransmitter.

FIG. 9 illustrates certain details of an embodiment of a mobile basestation for use with a utility locator and transmitter.

FIG. 10 illustrates certain details of methods and apparatus forprocessing GPS signals in a utility locator system.

DETAILED DESCRIPTION Overview

The present disclosure relates generally to devices and systems foridentifying hidden or buried utilities, such as underground water lines,sewer lines, gas lines, power lines, and the like. A mobile base stationmay be used with one or more portable utility locators to determine areference location and to aid in determining the location of aparticular locator during operation, as well as receive informationassociated with located utilities for storage and/or retransmission toother devices or systems.

For example, in one aspect, the disclosure relates to a mobile basestation for use in a buried utility locator system. The mobile basestation may, for example, include a vehicle, a plurality of antennasdisposed on the vehicle including a GPS antenna, and WLAN antenna, aplurality of receivers coupled to corresponding ones of the plurality ofantennas, a processing element configured to communicate with ones ofthe plurality of receivers, one or more utility locators, one or moreutility locator transmitters. The base station may further include apower supply subsystem for providing electrical power for the processingelements and plurality of receivers.

The vehicle may, for example, be a truck with a cap-type structuredisposed on a bed of the truck. The antennas may be disposed on thecap-type structure. The plurality of receivers and processing elementmay be disposed within the cap-type structure or may be coupled to thecap-type structure. The cap-type structure, receivers, and/or processingelement are configured to be rollably or slidably removable from thetruck.

The base station may, for example, further include a sensor suitecomprising one or more of a multi-axis accelerometer, a multi-axiscompass sensor, a multi-axis gyroscope, a barometer, a light sensor, anda temperature sensor. The sensors may be coupled to the processingelement for providing sensor output data to the processing element andassociating the sensor data with data provided to the processing elementfrom the one or more utility locators.

The GPS receiver may, for example, determine information from GPSsignals received at the GPS antenna and sends the determined informationto the one or more utility locators and/or to one or more utilitylocator transmitters. The determined GPS information may include timinginformation. The determined information may include positionalinformation associated with a position of the mobile base station. Thebase station may provide real time kinetic (RTK) data to the one or moreutility locators.

In another aspect, the disclosure relates to a utility locating system.The utility locating system may, for example, include a mobile basestation. The mobile base station may include a vehicle, a plurality ofantennas disposed on the vehicle including a GPS antenna, and WLANantenna, a plurality of receivers coupled to corresponding ones of theplurality of antennas, a processing element configured to communicatewith ones of the plurality of receivers, one or more utility locators,and one or more utility locator transmitters, and a power supplysubsystem for providing electrical power for the processing elements andplurality of receivers. The system may further include one or moreutility locators configured to communicate with the mobile base station.The system may further include one or more utility locator transmittersconfigured to communicate with the mobile base station.

Various additional aspect, features, and functionality are furtherdescribed below in conjunction with the appended Drawings.

The disclosures herein may be combined in various embodiments with thedisclosures in co-assigned patents and patent applications, includingtransmitter and locator devices and associated apparatus, systems, andmethods, as are described in U.S. Pat. No. 7,009,399, entitledOMNIDIRECTIONAL SONDE AND LINE LOCATOR, issued Mar. 7, 2006, U.S. Pat.No. 7,443,154, entitled MULTI-SENSOR MAPPING OMNIDIRECTIONAL SONDE ANDLINE LOCATOR, issued Oct. 28, 2008, U.S. Pat. No. 7,518,374, entitledRECONFIGURABLE PORTABLE LOCATOR EMPLOYING MULTIPLE SENSOR ARRAY HAVINGFLEXIBLE NESTED ORTHOGONAL ANTENNAS, issued Apr. 14, 2009, U.S. Pat. No.7,288,929, entitled INDUCTIVE CLAMP FOR APPLYING SIGNAL TO BURIEDUTILITIES, issued Oct. 30, 2007, U.S. Pat. No. 7,276,910, entitled ACOMPACT SELF-TUNED ELECTRICAL RESONATOR FOR BURIED OBJECT LOCATORAPPLICATIONS, issued Oct. 2, 2007, U.S. Pat. No. 7,990,151, entitledTRI_POD BURIED LOCATOR SYSTEM, issued Aug. 2, 2011, U.S. Pat. No.7,825,647, entitled COMPACT LINE ILLUMINATOR FOR LOCATING BURIED PIPESAND CABLES, issued Nov. 2, 2010, U.S. Pat. No. 8,264,226, U.S. Pat. No.7,619,516, entitled SINGLE AND MULTI-TRACE OMNIDIRECTIONAL SONDE ANDLINE LOCATORS AND TRANSMITTERS USED THEREWITH, issued Nov. 17, 2009,U.S. Pat. No. 8,264,226, entitled SYSTEM AND METHOD FOR LOCATING BURIEDPIPES AND CABLES WITH A MAN PORTABLE LOCATOR AND A TRANSMITTER IN A MESHNETWORK, issued Sep. 11, 2012, United States Provisional PatentApplication entitled OMNIDIRECTIONAL SONDE AND LINE LOCATOR, issued Mar.7, 2006, U.S. Pat. No. 8,248,056, entitled A BURIED OBJECT LOCATORSYSTEM EMPLOYING AUTOMATED VIRTUAL DEPTH EVENT DETECTION AND SIGNALING,issued Aug. 21, 2012, U.S. Provisional Patent Application Ser. No.61/618,746, entitled DUAL ANTENNA SYSTEMS WITH VARIABLE POLARIZATION,filed Mar. 31, 2012, U.S. patent application Ser. No. 13/851,951, filedMar. 27, 2013, entitled DUAL ANTENNA SYSTEMS WITH VARIABLE POLARIZATION,U.S. patent application Ser. No. 13/570,211, entitled PHASE-SYNCHRONIZEDBURIED OBJECT LOCATOR APPARATUS, SYSTEM, AND METHODS, filed Aug. 8,2012, U.S. patent application Ser. No. 13/469,024, entitled BURIEDOBJECT LOCATOR APPARATUS AND SYSTEMS, filed May 10, 2012, U.S. patentapplication Ser. No. 13/676,989, entitled QUAD-GRADIENT COILS FOR USE INA LOCATING SYSTEM, filed Nov. 11, 2012, U.S. patent application Ser. No.13/894,038, filed May 14, 2013, entitled OMNI-INDUCER TRANSMITTINGDEVICES AND SYSTEMS, U.S. patent application Ser. No. 13/841,879, filedMar. 15, 2013, entitled GROUND-TRACKING SYSTEMS AND APPARATUS, U.S.patent application Ser. No. 13/787,711, filed Mar. 6, 2013, entitledDUAL SENSED LOCATING SYSTEMS AND METHODS, U.S. patent application Ser.No. 12/947,503, entitled IMAGE BASED MAPPING LOCATING SYSTEM, filed Nov.16, 2010, and U.S. Provisional Patent Application Ser. No. 61/485,078,entitled LOCATOR ANTENNA CONFIGURATION, filed on May 11, 2011. Thecontent of each of these applications is incorporated by referenceherein in its entirety (these applications may be collectively denotedherein as the “incorporated applications”).

The following exemplary embodiments are provided for the purpose ofillustrating examples of various aspects, details, and functions of thepresent disclosure; however, the described embodiments are not intendedto be in any way limiting. It will be apparent to one of ordinary skillin the art that various aspects may be implemented in other embodimentswithin the spirit and scope of the present disclosure.

EXAMPLE EMBODIMENTS

Attention is directed to FIG. 1 which illustrates details of anexemplary embodiment 100 of a utility locating system mobile basestation (also denoted herein as a “mobile base station” or just “basestation” for brevity) in the form of a vehicle including a cap-typestructure 120 mounted in the bed of a pickup truck 105 bed as shown,along with associated elements as further described below.

The cap structure may be metallic, plastic, fiberglass, or othermaterials or combinations of materials and may be shaped to mount invarious types of truck beds or may be of a standardized shape and sizeto provide a universal mount.

Various elements may be mounted on or within the vehicle, such as on thecap structure, or may be electrically or optically coupled to the capstructure. For example, as shown in FIG. 1, various antennas may bemounted on the top (as shown) or sides or within the cap structure inalternate embodiments. Antennas may include one or more GPS antennas142, which may be coupled to one or more GPS receiver modules (asfurther illustrated as element 930 of FIG. 9) which may be mounted on orwithin the cap structure. Additional antennas may include one or morewide area network (WAN) antennas 146 and associated receivers ortransceivers 176, as well as one or more wireless local area network(WLAN) antennas 144 and associated transceivers 174. The WAN antennasmay be coupled to networks such as cellular data, Wi-Max, or other metroor wide area wireless networks (shown via wireless network hub 370 ofFIG. 3), which may be further coupled to the Internet to facilitate datatransfer to other Internet-connected server systems and/or databases,such as remote server system 380 of FIG. 3.

Inputs and output from the receivers or transceivers of the variousantennas may be coupled to one or more processing elements on or withinthe mobile base station, such as processing element 160 as shown inFIG. 1. The one or more processing elements may include software andhardware to perform the various control, communication, signalprocessing, and other functions described subsequently herein, such asprocessing of GPS signals to determine enhanced location information,generation of correction signals, control of communication between themobile base station and other system devices such as utility locator (asshown in FIGS. 3 and 4) and transmitters (as shown in FIGS. 3 and 4).

The one or more processing elements may control overall operation of themobile base station and its various elements as described subsequentlyherein. The one or more processing elements may include or be coupled tomemory or databases to store data such as raw or processed GPS data,detected utility data from the one or more locators, transmitter outputsignals or control signals, environmental conditions, images or videos,mapping data or information, geographic images, and/or other data orinformation collected during locate operations. A driver dispatch device111, such as a notebook, tablet, smart phone, or other electroniccomputing device may be disposed on or within the truck 105 cab or on orwithin the cap 120 or mounted elsewhere on the vehicle or mobile basestation to allow an operator to communicate with the mobile base stationand/or remote server system or dispatcher.

Some embodiments may include an imaging system for capturing images orvideo in an area where the mobile base station is being used ortransported to. This may be done with a camera head 150, which may be anomnidirectional or panoramic camera array or rotating camera system tocapture images or video over wide angles or throughout a 360 degreerange about the mobile base station. The camera head 150 may be coupledto the processing element and database or other memory storage withinthe cap 120 to tag the captured images or video with metadata such astime tags, location tags (e.g., based on location information determinedthrough a GPS or other GNSS or terrestrial positioning system orinertial positioning system), locate operation tags with data related toa locate operation being performed, such as operator name, type ofutility, customer information, and the like. A camera system includingLIDAR or other technologies, such as, for example, a system similar toGoogle's StreetView camera system, may be used to capture the images,which may then be stored and post-processed to provide a continuousstitched image view of the area where the mobile base station isoperating or is transported through.

The mobile base station may include a power supply sub-system 190, whichmay be disposed on or within the cap 120 and/or associated vehicle 105.Power may be supplied to the mobile base station using various powersupply elements such as vehicle power (e.g., from alternators,regenerative power, vehicle batteries, etc.) or through external powersuch as from a photovoltaic panel 192, a gas or diesel generator (notshown), wind turbine (not shown), additional batteries (not shown),inverters (not shown), fuel cells (not shown), or other power sourcesthat are known or developed in the art.

In some embodiments, cap 120 as shown in FIG. 1 may be configured withslides or rollers to allow the cap and associated elements mounted on orwithin the cap to roll or slide off the truck bed for use on the groundor other surfaces. This may be useful in applications where a mobilebase station needs to be located in a well-defined reference location,or when the mobile base station needs to be used on site for a certainperiod of time without having the truck out of service.

The mobile base station and/or associated system elements such aslocators or transmitters may also include a sensor suite, which mayinclude sensors such as a multi-axis (e.g., three axis) accelerometer, amulti-axis compass sensor, multi-axis gyroscopes or gyroscopic sensors,barometers (for altitude sensing, etc.), light sensors, humiditysensors, temperature sensors, wind sensors, weather sensors (e.g., windspeed, rainfall, temperature, humidity, etc.), received signal strengthindicators (RSSI) sensing, Wi-Fi sensors, cellular, or other wirelesslink sensors, and the like.

Additional elements on the mobile base station may include devices suchas ground penetrating radar (GPR) systems 134 (including antennas andassociated electronic circuitry modules), electromagnetic locatingarrays 132 (including antennas and associated circuitry, which mayinclude one or more locators, such as, for example, four locators on thecorners of the mobile base station or truck or trailer to detect buriedpower lines or other current-carrying utilities under the street orground on which the truck is operating as shown), sonar systems (notshown), optical sensing systems, and the like.

In operation, one function of the mobile base station may be todetermine location information regarding its current location to a highdegree of accuracy. This information may then be communicated to acorresponding locator to allow the locator to determine highly accuraterelative or absolute location information. High accuracy locationinformation may be done at the mobile base station by, for example,using multiple GPS antennas and receivers and integrating received GPSsignals over periods of time to improve accuracy. For example, fourspaced-apart GPS antennas, such as antennas 142 as shown in FIG. 1 (orin other configurations, fewer or more antennas, such as, in oneembodiment a dual GPS antenna array as described in the incorporatedapplications), may be used, along with a corresponding receiver orreceivers. Other technologies, such as differential GPS, real timekinetic (RTK) terrestrial positioning system signaling (RSSI),terrestrial positioning systems such as are described in, for example,United States Patent Publication 2013/0169484, entitled WIDE AREAPOSITIONING SYSTEMS AND METHODS, which is incorporated by referenceherein, and the like may be used to obtain precise location informationfor the mobile base station. Further, in addition to determininglocation information at a locate site, the mobile base station may beconfigured to allow the GPS sub-system, typically using multiplespaced-apart antennas, to run continuously during movement of the truckfrom one site to another to track location and improve positioningaccuracy. The mobile base station may also be used, as describedsubsequently herein, to provide signals to associated utility locatorsto allow the locators to determine their location, either in relative(with respect to the base station) or absolute terms, with a high degreeof accuracy. In some embodiments, multiple wireless link antennas may beused on mobile base station embodiments to use radio direction finding(RDF) techniques to determine positional information.

In addition to providing precision location information, such as in theform of an RTK or RTK-like system, the mobile base station may be incommunication with one or more utility locators and/or one or moreutility locator transmitters at the locate site, such as through use ofa WLAN communication link or other short-range communication link suchas an ISM band link, Bluetooth, or other short-range communication linkssuch as optical or ultrasonic links. Examples of such a configurationare shown in further detail in FIG. 3 and FIG. 4. In addition, themobile base station may be in communication, via a WAN communicationlink, with remote server systems and databases, such as through cellularnetworks or other WAN networks and the Internet, to transfer data fromthe locate operation to a remote server and database. In someembodiments, the mobile base station may include one or more directionalantennas to extend the wireless communication range to a locatingreceiver (e.g., at a particular operating location). The directionalantenna may be configured to be set by a user and/or remotely controlledby the user, such as when the user is moving around an extended area, soas to maintain coverage during movement. Directional antennas may beconfigured to actively point or aim towards a roving locating receivervia mechanical scanning or electronic scanning using phased array orother direction-finding techniques as are known or developed in the art.Directional antenna configurations may also be combined with RDFtechniques as described above in some embodiments.

FIG. 2 illustrates details of another embodiment of a mobile basestation system 200 in the form of a trailer 207 with a cap 220 mountedon or integral with the trailer. The various elements shown in FIG. 2may be the same as or similar to equivalently numbered elements ofFIG. 1. Similar elements may be included in the trailer cap 220including one or more GPS antennas 242 and associated GPS receivers(illustrated in further detail in FIG. 9), WAN antennas 246 andassociated transceivers 276, WLAN antennas 244 and associatedtransceivers 274, camera heads 250, GPR systems 234, EM antenna arraysystems 232, and the like. The trailer 207 may be towed with a pickuptruck 205 or other vehicle capable of towing a trailer. The truck and/ormobile base station may include a driver dispatch device 211, such as atablet, notebook, smart phone, or other electronic computing system,which may be in communication with processing element 260 of the mobilebase station in a similar fashion to the configuration shown in FIG. 1.A plug or other connection mechanism may be included on the trailer 207and truck 205 to connect the dispatch device 211 to the mobile basestation 200.

FIG. 3 illustrates details of an embodiment of a location system 300including a mobile base station 100, such as shown in FIG. 1, in anexample locate operation. The illustrated system includes a truck 105with an attached cap 120 and associated elements as shown in FIG. 1,including one or more processing elements 160 internal to the cap. Themobile base station may include a WAN module with an attached WANantenna 146 and receiver, transmitter, and/or transceiver 176 forcommunicating with a wireless network hub 370, such as via a cellular orother wide area network (or, in some implementations, a WLAN, such as alocal Wi-Fi network, or via a wired network if wired communicationconnections are available). A remote server system 380, which mayinclude one or more processing element 384 to post-process received datafrom locate operations, as well as a database 386 and a networkconnectivity module 382, may be coupled to the mobile base stationthrough a network connection, such as through the cellular network andInternet.

Various locate site configurations are possible; however, for purposedof explanation, the following example configuration is provided. Asshown in the example site of FIG. 4, there may be a power or telephonepole 305 and a utility cabinet 307, to which a first utility locatortransmitter 340-1 may be coupled to generate current for detection by alocator, such as through a clamp 343. Another connection may include afire hydrant 303 or other pipe terminal where a second transmitter 340-2may be attached to couple currents so as to induce magnetic fields 308in an underground pipe 304 electrically coupled to the hydrant. Autility locator 330 is shown sensing the magnetic fields from the buriedwater pipe 304. The utility locator may be any of a variety of utilitylocators. In an exemplary embodiment, the utility locator may be amulti-frequency locator as described in, for example, the incorporatedapplications.

The mobile base station may include multiple GPS antennas, such as, forexample, the four spaced-apart antennas as shown in FIG. 1, to provideenhanced GPS location accuracy. In addition, transmitters 340-1 and340-2, as well as locator 330, may include GPS antennas and receivers(e.g., 342-1, 342-2, and 332) so as to generate data output at the GPSreceivers coupled to the antennas. In operation, the mobile base stationGPS antennas and receivers may be kept operational or “hot” at alltimes. In a typical GPS system, accuracy that can be obtained may be inthe 2-3 meter range. However, if output data from the GPS receivers iscollected and stored, the GPS output data may later to post-processed toimprove accuracy, in some cases substantially. GPS provides veryaccurate time information, which can be used to synchronize datacollected from GPS receiver outputs across devices (e.g., the basestation, transmitters, locators, and/or other coupled devices). In oneexemplary embodiment, the GPS antennas may be configured as described inco-assigned U.S. patent application Ser. No. 13/851,951, filed Mar. 27,2013, entitled DUAL ANTENNA SYSTEMS WITH VARIABLE POLARIZATION, which isincorporated by reference herein.

In typical applications, it is desirable to have a high accuracyreal-time display, on or at the locator 330, of movement (e.g., a highprecision system to show that the locator is moving accurately, forexample, by 30 cm forward and 30 cm backwards). If the locators andtransmitters are configured as multi-frequency locate systems, such asdescribed in, for example, co-assigned U.S. patent application Ser. No.13/894,038, filed May 14, 2013, entitled OMNI-INDUCER TRANSMITTINGDEVICES AND SYSTEMS, and U.S. patent application Ser. No. 13/787,711,filed Mar. 6, 2013, entitled DUAL SENSED LOCATING SYSTEMS AND METHODS,both of which are incorporated by reference herein, substantial data maybe collected and associated with precise motion detection. In a typicalembodiment, the motion of the locator may be determined in a relativesense, e.g., relative to the mobile base station, which may be at afixed position and may use multiple GPS antennas to determine positionaccurately, and/or store GPS receiver output data for post-processinglater to determine precision location information. GPS receivers aloneare unable to determine accuracy to this degree, and will reflectmovement in position when the associated device is placed at rest.However, through use of Real Time Kinetic or similar or analogousprocessing, relative local position information may be dramaticallyimproved.

All of the devices (e.g., transmitters 340, locator 330, and mobile basestation 100) shown in FIG. 3 may include a sensor suite, which mayinclude inertial sensors such as three-axis accelerometers, three-axiscompass sensors, GPS or other global satellite navigation system (GNSS)receivers, terrestrial positioning system receivers, gyroscopic sensors,and the like. The mobile base station may be configured as a Wi-Fi (orother WLAN) hub, such as via antenna 144 and its associated transceiver(not shown), so that the mobile base station may send positioninformation to the locator (along with, for example, the transmitters,which are typically in a fixed position, also sending information to thelocator, where the locator may use its own GPS receiver output, plus thecorrection information sent by the mobile base station and/ortransmitters, to determine enhanced position and/or accurate relativeposition (relative to the base station and/or transmitters). Systemssuch as SBAS and others can also be used, however, while SBAS andsimilar systems provide potentially improved accuracy, it may not besufficient for typical locate operations.

GPS receivers can provide both binary data and carrier phase information(e.g., for each satellite the receiver is listening to), which may be inthe form of Sirf4 binary data (based on one particular IC module) orother similar or equivalent data that includes positional information,satellite information, as well as carrier phase. Examples of availabledata are described in FIG. 10. Based on device sensors such asaccelerometers in the mobile base station and/or transmitters, motion(or lack thereof) may be determined. Moreover, through use of multiplefixed elements (e.g., a mobile base station and one or moretransmitters, or through use of multiple mobile base stations), accuracymay also be further enhanced through processing of signals received fromeach of the fixed position devices. Details of one embodiment of thisprocessing and corresponding modules to generate an RTK solution areillustrated and described subsequently herein with respect to FIG. 10.

Using all of this information, the position of the locator may beaccurately determined to, for example, the cm level. This may be done byeither processing the data received from one or more fixed elements inthe locator directly, or through sending data from the fixed elements tothe base station, processing the data in the base station, and thentransmitting processed information as a correction signal or as relativeor absolute position data to the locator from the mobile base station.

In the example of FIG. 3, all of the elements (transmitters, mobile basestation, and locators) may have GPS antennas and receivers runningcontinuously. The devices may be configured so that only the GPSelements are kept running, and there may be a docking power station orother power supply device in the mobile base station or truck to powerthe devices when not in field use. For example, the transmitters 340 andlocator 330 may be stored with the cap 120 and plugged into a powersource therein. If the cap is made of an appropriately RF transparentmaterial, the GPS antennas on each of the devices may continue toreceive signals when stored inside the cap.

Raw data streams from the GPS receivers (e.g., determined locationinformation and other raw data, including carrier phase, etc.) may besent from the two transmitters 340-1 and 340-2 and the mobile basestation 100, via communication links 345-1, 345-2, and 325,respectively, to the locator 330 as shown in FIG. 3. The locator 330then receives and processes this data, along with data from its own GPSreceiver output, to determine enhance accuracy location information.This allows displaying both the utility information (e.g., magneticallysensed information as is done in a typical locator), along with accuratelocation information. The display may include maps, local area imagery,other data or information, or combinations of these. The GPS data mayalso be stored for later post-processing to increase accuracy. In thatcase, data may be sent from the locator to the mobile base station, andthen may be further transmitted via the wireless network hub 370 toremote server system 380, where it may be post-processed in a processingelement 384 and stored in a database 386. The post-processed data may becombined with maps, images, or other information to generate highlyaccurate maps and graphics showing buried utility information. Thisinformation may also be transmitted back to locators for future displayuse. In some embodiments, GPS compass techniques may be used toaccurately determine the orientation of the base station. In someembodiments, offset pairs of GPS antennas and corresponding receiversmay also be used on the receiver and/or transmitter to further improveorientation accuracy compared to magnetic compass data.

FIG. 4 illustrates another embodiment of signal transmission andprocessing in a utility locating system with a mobile base station. Inthe example of FIG. 4, the transmitters 340-1 and 340-2 send GPSreceiver output data, via communication links 445-1 and 445-2, to themobile base station 100 via receive antenna 144. Signal processing ofthe GPS data from the transmitters, along with GPS data from the one ormore GPS antennas and/or receivers in the mobile base station, may bedone at the mobile base station, with correction data and/or absolute orrelative position data then sent via communications link 435 to thelocator 330.

In the locator 330, a Kalman filter may be run with the GPS data andinertial or other sensor data to provide further accuracy. With multiplefixed position GPS receivers (e.g., a mobile base station and one ormore transmitters) low cost GPS receivers may be used, rather than highcost, high accuracy GPS receivers, which are the standard solution forhigh accuracy measurements.

In a typical embodiment, data may be collected from the multiple systemelements (e.g., one or more transmitters, the mobile base station, andthe locator(s)) with the data then sent to the remote server system 380for post-processing, which may be done later. For example, when theprecise ephemeris data is published later (e.g., days or weeks aftersignal transmission) for the GPS satellites, the data collected from thesystem elements may be further post-processed to further increaseaccuracy. CORS station information may also be used to post-process theGPS data in closer to real-time. This post-processing may then becombined with locator data to generate precise mapping informationassociated with detected buried utilities, with the data stored in theremove server system.

FIG. 5 illustrates details of an embodiment 500 of a process forprocessing data from multiple GPS receivers to generate enhancedlocation information in a utility locator. Process 500 may begin atstage 510, where GPS data, including carrier phase information, from oneor more utility locating system devices, such as one or more utilitylocating transmitters, is sent from the devices to a utility locator andreceived at the locator. The data may be sent by wireless communicationlinks such as Bluetooth, ISM band links, WiFi links, optical links,infrared links, or other local wireless data communication links. Insome embodiments, the data may be sent via a wired connection to thelocator, however, due to the desired mobility of the locator this istypically not desirable. At stage 520, data from one or more GPSreceivers, typically from an array of two or more GPS receivers,including carrier phase information, may similarly be sent from a mobilebase station to the utility locator. At stage 530, the received GPS datamay be applied, along with locally generated GPS data and/or locallygenerated sensor data, such as accelerometer, compass sensor, or otherlocal data, to a Kalman filter or other similar or equivalent processingalgorithm. Additional inputs may include ground tracking data, such asoptical ground tracking techniques as are described in the incorporatedapplications, including, for example, co-assigned U.S. patentapplication Ser. No. 13/841,879, filed Mar. 15, 2013, entitledGROUND-TRACKING SYSTEMS AND APPARATUS, which is incorporated byreference herein.

At stage 540, the Kalman filter output, representing either enhancedrelative (with respect to the mobile base station) or absolute locationinformation, may be generated as a function of the Kalman filter outputand may be stored in a memory and/or transmitted to other utility locatesystem devices. At stage 550, the location information may be displayedon a display element of the locator, such as on a display screen orother output device. The display may combined location and/or motioninformation with information associated with one or more detected buriedutilities. For example, the location information may be shown on a gridor other reference relative to lines or other symbols representing thedetected utilities. Maps, images, or other graphics may be overlaid orregistered with respect to the detected utilities using the determinedlocation information.

In some embodiments, map data and/or images corresponding to an area inwhich a locate operation is being performed may be stored in the locatoror in the mobile base station or sent from the remote server system.Maps or images may be rendered on a display of the locator and/or mobilebase station or associated device, such as the dispatch device 111 ofFIG. 1, and may be dynamically aligned with locator data or information,such as determined locator position and/or information associated withidentified buried utilities, ground features, camera images or video,and the like. In locator embodiments including a camera disposed on orcoupled to the locator, captured images or video may be associated withthe map data, positional data, and/or other locator data or informationand may be displayed, stored, transmitted to the mobile base stationand/or remote server system, or otherwise processed for future use,display, data mining, aggregation, or mapping use. Camera images orvideo may be combined with other information as described herein and maybe stored, tagged, transmitted, and the like along with the otherdescribed data and information. In some embodiments, mobile base stationcamera systems, such as camera 150 as shown in FIG. 1, may be configuredto dynamically track the position of the locator, such as bycoordinating with directional antennas as described herein, or byoptically tracking the locator using an electromagnetic signal oroptical signal. For example, in some embodiments a locator may beconfigured with an LED or other optical output device that may generatea predefined flash sequence, color, wavelength of output light,brightness, etc. The camera may be configured with a processing elementto detect this light output and use it to track the locator and user.

FIG. 6 illustrates details of an embodiment 600 of a method forprocessing data from multiple GPS receivers to generate enhancedlocation information at a mobile base station, which may be communicatedto an associated utility locator. Process 600 may begin at stage 610,where GPS data, including carrier phase information, from one or moreutility locating system devices, such as one or more utility locatingtransmitters, is sent from the devices to the mobile base station andreceived at the mobile base station. The data may be sent by wirelesscommunication links such as Bluetooth, ISM band links, WiFi links, orother local wireless data communication links. In some embodiments, thedata may be sent via a wired connection to the mobile base station. Atstage 620, data from one or more GPS receivers, typically from an arrayof two or more GPS receivers, including carrier phase information, maysimilarly be generated at the mobile base station. At stage 630, thereceived GPS data may processed along with the locally generated GPSdata to determine enhanced accuracy mobile base station locationinformation. This information may be sent directly to a correspondinglocator or may be used to generate correction data at stage 640. Thecorrection data may be sent as a correction signal at stage 650 to beused by the locator to correct locally received GPS data so as toprovide enhanced relative location or absolute location information.This may be done by, for example, applying the correction data to alocally executed Kalman filter at the locator, where it may be combinedwith locally generated GPS data and/or other locally generated sensordata, such as accelerometer or compass sensor data. The locator may alsosend raw GPS data and/or sensor data to the mobile base station, and/ormay send corrected relative or absolute location information and/orinformation associated with detected utilities or other sensedinformation.

FIG. 7 illustrates certain details of utility locator embodiment 330 ofFIG. 3 or FIG. 4. Various additional details of locators as may becombined with the details of FIG. 7 are detailed in the variousincorporated utility locator applications described previously herein.Utility locator embodiment 330 may include magnetic field antennas orantenna arrays 710, which sense magnetic fields from hidden or buriedutilities (e.g., as illustrated in FIG. 3 and FIG. 4) and provideantenna output signals to a signal processing circuit 712, whichincludes analog and digital circuitry to process the received magneticfield signals 308 and determine information associated with the utility,such as depth, orientation, type of utility, other utilities in thearea, and the like. One or more processing elements 160 may be includedin the locator to provide various control, signal processing, display,communication, and other functions as described herein. One or morememories 770 may be coupled to the processing elements to storeexecutable code and data. The memories 770 may include storedinformation such as map data, images, video, as well as positional dataand information and buried utility data and information. The locator 330may include one or more user interfaces 750, which may include keys orswitches, displays, such as LCD or other output display devices forrendering images, maps, buried utility information, positionalinformation, and/or other data or information as described herein.Additional user interface elements may include audio output devices,microphones, mice or joysticks or other manual user interface devices,headphones or headphone jacks, LED or outer visual output elements, andthe like.

The locator 330 may include one or more GPS antennas 332 as well as oneor more GPS receiver modules 730, which may provide output GPS data,including positional data and carrier phase data as well as other dataas described herein, to the processing element 760 for performing signalprocessing as described herein to determine accurate positionalinformation. In some embodiments, the GPS data may be sent from thelocator 330 to a corresponding mobile base station, where the positionalsignal processing may be performed (e.g., as shown in FIG. 4). In otherembodiments (e.g., as shown in FIG. 3), the locator 330 may directlyperform signal processing from received base station signals providedfrom a mobile base station and/or additional fixed references or basestations such as transmitters 340. Data may be sent from the locator tothe mobile base station, and/or received from the mobile base stationand/or transmitters, through WLAN antenna 334 and wireless local areanetwork interface module 740, such a via communication links 332, 325,and/or 435 as shown. Additional data may be collected at the locator,such as inertial data, optical data (e.g., optical ground tracking data,etc.), compass or other positioning sensor data, and the like in one ormore sensor modules 720. Environmental conditions and/or physicalparameters may be collected in one or more environmental sensor modules722, such as temperature information, pressure information (e.g.,barometric pressure, humidity, etc.). Signal processing such as isdescribed with respect to FIG. 10 may be implemented in the locator 330or in a mobile base station or a remote server system.

FIG. 8 illustrates certain details of utility transmitter embodiment 340of FIG. 3 or FIG. 4. Various additional details of transmitters as maybe combined with the details of FIG. 8 are detailed in the variousincorporated utility transmitter applications described previouslyherein. Utility transmitter embodiment 340 may include an output currentgeneration circuit 810 and associated coupling circuit 815 (for director inductive or capacitive current coupling) to generate current signalsto be applied to a buried utility and couple the signals to the utilityso as to generate magnetic field lines (e.g., as shown in FIG. 3 andFIG. 4). When the transmitter is in use, it is typically placed at afixed location, which can be sensed by, for example, onboard sensors. Inthis condition, the transmitter can function as an additional basestation and may send signals to either an associated locator, anassociated mobile base station, another transmitter, or combinations ofor all of these system elements.

One or more processing elements 860 may be included in the transmitterto provide various control, output current generation, display,communication, positioning signal processing, and other functions asdescribed herein. One or more memories 870 may be coupled to theprocessing elements to store executable code and data. The memories 870may include stored information such as data associated with outputcurrent signals and signal synchronization, such as time or phasesynchronization, which may be communicated with an associated locatervia a wired or wireless connection (not shown). The transmitter 340 mayinclude one or more user interfaces 850, which may include keys orswitches, displays, such as LCD or other output display devices fordisplaying information such as output frequencies, signal patterns,current levels, and/or other data or information as described herein.Additional user interface elements may include audio output devices,microphones, mice or joysticks or other manual user interface devices toallow users to enter information into the transmitter, along with visualoutput elements, audio output elements, and the like.

The transmitter 340 may include one or more GPS antennas 342 as well asone or more GPS receiver modules 830, which may provide output GPS data,including positional data and carrier phase data as well as other dataas described herein, to the processing element 860, and for furthertransmission to associated mobile base stations, locators, and/or othertransmitters. In some embodiments, the GPS data may be sent from thetransmitter 340 to a corresponding mobile base station, where positionalsignal processing may be performed (e.g., as shown in FIG. 4). In otherembodiments (e.g., as shown in FIG. 3), the transmitter 340 may sendsignals directly to a corresponding mobile base station. Data may besent from the transmitter to the mobile base station, and/or receivedfrom the mobile base station and/or other transmitters or locators,through WLAN antenna 344 and wireless local area network interfacemodule 740, such a via communication links 345 and/or 445 as shown.

Additional data may be collected at the transmitter, such as inertialdata, compass or other positioning sensor data, and the like in one ormore sensor modules 820. Environmental conditions and/or physicalparameters may be collected in one or more environmental sensor modules822, such as temperature information, pressure information (e.g.,barometric pressure, humidity, etc.). GPS, other sensor, and/orenvironmental data may be sent from the transmitter to a correspondinglocator, mobile base station, or both, where further signal processing,such as described with respect to FIG. 10, may be implemented.

FIG. 9 illustrates certain details of mobile base station embodiment 100or 200 as described previously herein with respect to FIG. 1 throughFIG. 4. Mobile base station embodiment 100 (or 200) may include variousinput elements as described previously herein, such as one or morecamera modules 150 for generating omnidirectional or panoramic images orvideo, a ground penetrating radar (GRP) array and circuitry 134 forgenerating radar imagery during movement of the mobile base station orwhen fixed in position, an electromagnetic field antenna array andassociated circuitry 132 for sensing utilities, such as energized powercables, during movement of the mobile base station or when at a fixedlocation, as well as other elements as described previously herein. Apower supply subsystem 190 may be used to power the various elements ofthe mobile base station, and may be any of a variety of power supplyelements, such as vehicle or additional batteries, inverters,photovoltaic panels, wind power turbines, fuel cells, generators,alternators, and the like.

One or more processing elements 160 may be included in the mobile basestation to provide various control, signal processing, display,communication, and other functions as described herein, includingreceiving information from associated transmitters and locators andprocessing positional data to determine accurate positional information,as well as communicating such information or correction signals tocorresponding locators. One or more memories 970 may be coupled to theprocessing elements to store executable code and data. The memories 970may include stored information such as map data, images, video, as wellas positional data and information and buried utility data andinformation. The pay data, images, and other data may be communicated toa corresponding locator for display, storage, association with utilitydata, and the lie. The mobile base station 100 or 200 may include one ormore user interfaces 950, which may include keys or switches, displays,such as LCD or other output display devices for providing userinformation and receiving user input. Additional user interface elementsmay include audio output devices, microphones, mice or joysticks orother manual user interface devices, headphones or headphone jacks, LEDor outer visual output elements, and the like.

The mobile bases station 100 or 200 may include one or more GPS antennas142 as well as one or more GPS receiver modules 930, which may provideoutput GPS data, including positional data and carrier phase data aswell as other data as described herein, to the processing element 960for performing signal processing as described herein to determineaccurate positional information, or may transmit the output data to acorresponding locator. For example, in some embodiments, the GPS datamay be sent from the transmitter 340 to a corresponding locator, wherethe positional signal processing may be performed (e.g., as shown inFIG. 3). In other embodiments (e.g., as shown in FIG. 4), the locator330 may send its positional data to the mobile base station where thesignal processing may be performed (additional data from one or moretransmitters may also be received and used in the signal processing,such as shown in FIG. 3). Data may be sent from the mobile base stationand/or received at the mobile base station and/or transmitters, throughWLAN antenna 144 and wireless local area network interface module 174,such a via communication links 445 and/or 435 as shown. Additional datamay be collected at the mobile base station, such as inertial data,optical data (e.g., optical ground tracking data, etc.), compass orother positioning sensor data, and the like in one or more sensormodules 922. Environmental conditions and/or physical parameters may becollected in one or more environmental sensor modules 922, such astemperature information, pressure information (e.g., barometricpressure, humidity, etc.). Signal processing such as is described withrespect to FIG. 10 may be implemented in the mobile base station 100 or200 or in a mobile base station or a remote server system, which may becommunicatively be coupled through WAN antenna 146 and wireless widearea network interface module 176 as shown.

FIG. 10 illustrates details of one embodiment 1000 of a signalprocessing flowchart as may be used to generate enhanced locationinformation using GPS received output data including carrier phase andother parameters.

Flowchart 1000 highlights several example stages of data processing andalgorithms that comprise one embodiment for determining an RTK solution,such as at a mobile base station or, in some embodiments, in a locatoror a remote server system or other electronic computing system. Thefollowing stages are described in further detail below: Input Data,Screen/Group/Sync, Clock Jump Detection/Repair, Cycle SlipDetection/Repair, Point Positioning Solution, Initial BasestationPosition, Formulation of Double Difference Observations/Covariance, RTKProcessing (Float Solution, Integer Least Squares Ambiguity Resolution,Fixed Solution), and Multi-Basestation/Inertial Solution Verification.The various illustrated blocks of FIG. 10 represent Data,Estimates/Constants, Algorithms, Data Fusion, or Solutions/Outputs.

Input Data

The input data may be comprised of the following: one or more roverreceiver data, one or more basestation receiver data, INS sensor data,range measurement data, and camera data (e.g., for optical groundtracking as described in the incorporated applications). For a real-timeimplementation of this system a radio or optical datalink would benecessary between receiver(s)/sensor(s) so data could be exchanged andcaptured in the processing element(s). Example INS sensor data includes,for example, accelerometer data (e.g., single or multi-axis, such asthree axis, accelerometer sensors), single or multi-axis gyroscopicsensors, single or multi-axis compass sensors, MEMs sensor arrays, andthe like. Multiple data rates may be available/used for thesesensors/receivers. Dual frequency data may be collected by each GPSreceiver as well as multi-polarity antennas could capture differentpolarized data for groups of receivers.

RTK processing requires data from at least one rover receiver (e.g., alocator or other movable device) and one basestation receiver (e.g., oneor more mobile basestations or other fixed position devices such astransmitters, etc.). All other sensor/receiver data are optional for RTKbut may be used to further aid the system in more sophisticated methodsincluded in the system below. The starting position may be measures forthe receiver/rover (locator) and transmitter (base station) usingelectromagnetic antennas and compass/gyro/inertial navigation sensors,etc.

Screen/Group/Sync

Multiple requirements may be enforced on the data collected to ensurethe only appropriate data is used in the system. Data may be grouped bythe specific receiver/sensor platform to which it is associated (i.e.rover or basestation). Another grouping used for some GPS data is togroup data by the satellite to which it is associated. Some examples ofGPS data requirements are: minimum elevation angle, minimum SNR, andsatellite health. Finally, all GPS data sharing identical epochs shouldbe synchronized (between satellites and between receivers) to match eachother and for other sensors their time systems would be converted andinterpolated to line up with GPS time or vice versa.

Receiver Clock Jump Detection/Repair

Clock Jump Detection/Repair may be carried out on a per GPS receiverbasis as receiver clock jumps are receiver dependent. Clock jumps arestep-like jumps that affect both pseudorange and carrier phasemeasurements collected by GPS receivers. Detection of potential jumpsmay be carried out for each satellite. Only if all satellites beingtracked have jumps of roughly the same amount in pseudorange and carrierphase at exactly the same epochs can a receiver clock jump be fullyclassified. Monitoring of the estimated receiver clock bias (estimatedduring point positioning or through some other clock model) may be doneto further strengthen identify receiver clock jumps. Some GPS receiversalso report an estimated receiver clock bias directly which may be usedas well. Using a clock model to quantify the receiver clock jump istypically best, but it may also be calculated as some weighted averagebased on the observed jumps in pseudorange and carrier phase in all thesatellites being tracked. Once the clock jump is calculated it may thenbe removed from the pseudorange and carrier phase data at the affectedepochs.

Cycle Slip Detection/Repair

Cycle slip detection and repair may only be important if one is usingraw Carrier Phase data for receiver positioning (RTK, PPP, etc.), ascycle slips can affect Carrier Phase data. There are several methods fordetection and repair of cycle slips which only affect the Carrier Phasedata for GPS receivers. Some of these methods are based on multiple timedifferencing using Carrier Phase and/or Pseudorange and/or Doppler dataas well as polynomial curve fitting to estimate the cycle slip amount.These methods require a minimum number of epochs of continuous trackingdata in order to initialize so they are usually more suited to postprocessing. If dual frequency receivers are available there are easiermethods that may be used to compute the cycle slips. Also, there areeven least squares geometry based techniques that can be used on singlefrequency GPS data to estimate cycle slips. Another constraint is thatthe size of each cycle slip must be an integer. Raw Carrier Phase datawith cycle slips would have a characteristic jump in the data similar toa receiver clock jump except cycle slips are receiver and satellitedependent because they occur at the tracking loop level.

Initial Basestation Position

RTK systems use one or more stationary basestations from which arelative baseline position(s) is estimated for the rover(s) relative tothe basestation(s). The inherent relative baseline accuracy, as well asthe absolute accuracy of the rover's RTK position, is highly dependenton the absolute position of the basestation. Depending on whether thesystem is real-time or post processing there are several options forcalculating the basestation's absolute position. Post processing offersthe most flexible options, one of which is to average the Point Positionsolutions for all epochs for that basestation and use that as an initialbasestation position, depending on the standard deviation of the timehistory of the solution. Real-time applications could allow adjustmentsto the currently used initial basestation positions by considering thecurrent Point Positioning solution for the basestation's absoluteposition or a moving weighted average of a buffered list of previousPoint Positioning solutions.

Point Positioning

Point Positioning is one of the simplest forms of computing a GPSreceiver's absolute geodetic position. The basic requirements to computea Point Position solution are: raw Pseudorange data from four or moresatellites, estimated Ionosphere bias, estimated Satellite Orbits,estimated Troposphere bias, and estimated Satellite clock bias. Theseestimated biases/orbits can be calculated from multiple sources:ephemeris broadcast models (Saastamoinen, Klobuchar, etc.) or eveninterpolated from precisely generated orbit tables (SP3) or ionospheretables (IONEX) supplied by the IGS. Interpolating from the precise tabledata is only an option for post processing. There are several differentmodels that can be used to estimate the Troposphere (UNB3m, UNB, etc.)and Ionosphere biases. The basic outputs from a simple Point Positionsolution are the receiver's displacement from a user defined origin andthe receiver clock bias as well as the covariance matrix associated withthese estimated outputs. Not all Point Position solutions are the same;it is the solving of linearized (or nonlinear) equations in whichdifferent solution options differ. Some options include: standard leastsquare adjustment, weighted least squares adjustment, Kalman filter,extended Kalman filter, and INS aided Tight Integration (Kalman filterbased). Some Kalman filter solutions even estimate the Pseudorangebiases (such as Ionosphere, Tropospere, etc.) inside of its statevector. INS aided Tight Integration is a useful verification tool formonitoring the relative agreement between the standalone INS positionversus the Point Position solution based on the raw Pseudorange GPSdata.

Assumptions for the Above

It is assumed that the baseline between the base station(s) and rover(s)is small (under 20 km). Because of this, many of the errors associatedwith the observations can be considered to be identical for both thebase station(s) and the rover(s). These errors include atmosphericdelays, line of sight unit vectors.

Double Differences

The cycle slip corrected observations are then double differenced inpreparation for calculating a float solution. To achieve the doubledifference observations, cycle slip corrected observations are firstdifference across satellite pairs, and then those differences aredifferenced across receiver pairs. This double differencing processremoves various error factors from the observations including clockbiases and atmospheric delays. Double differenced unit vectors are alsocalculated using the line of sight angles of azimuth and elevation fromthe base station to each satellite. After a minimum of two epochs worthof double differenced observations have been made, the covariance ofthose measurements can be computed, and the float solution can then begenerated.

Float Solution

The float solution represents the double differenced number of cyclesbetween each satellite pair and receiver pair. These double differencednumbers of cycles is related to the double differenced observations andthe double differenced unit vectors through a well known linearizationof the observation model.

The linear system of equations has a set of known values (the doubledifferenced observations), linear coefficients (comprised of doubledifferenced unit vectors), and a set of unknowns which are: the floatbaseline vector relative to some user defined origin and the doubledifferenced float ambiguities. This float baseline vector gives therelative position of the rover receiver at that epoch relative to someuser defined origin, most commonly chosen as the basestation's absoluteposition. These linear equations may be solved using a variety ofmethods but the most common are adjusted least squares or Kalmanfiltering.

Integer Least Squares

The resulting double differenced float ambiguities should theoreticallybe integers, but due to residual errors and noise, these values will berational. The float ambiguities will therefore be used in one of twoways: it may be resolved to an integer form to be used in the RTKbaseline solution, or it may be used directly for the RTK baselinesolution.

In order to resolve the float ambiguities to integers, some form orinteger least squares must be used. Either the LAMBDA method or MLAMBDAmethod are generally recognized as superior integer least squaresapproaches for RTK applications, though any could be used. These methodsare well documented. Any integer least squares approach to be used inthis application takes the float ambiguities and their covariances asinputs and produces statistically optimal fixed (integer) ambiguitiesand their covariances as outputs.

These fixed ambiguities then undergo a verification process to ensurethat they are an improvement over the current set of ambiguities, whichmay either be the float ambiguities or another set of fixed ambiguitiesthat have previously been validated.

This validation process includes multiple processes to ensure that theoptimal set of ambiguities is selected for calculating the RTK solution.First, the covariances of the float ambiguities are analyzed to assurethat these values have settled to an appropriate level. If thecovariances have not settled yet, then the float solution is used whileits covariances continue to settle.

Next, the statistically optimal set of fixed ambiguities are compared tothe next most optimal set of fixed ambiguities. This process is known asa ratio test for fixed ambiguities. The sum of squared residual errorsis computed from each of those sets and if the ratio of those sums iswithin some defined threshold then this indicates that this set of fixedambiguities is an improvement on the float ambiguities. If the ratio isoutside of the threshold, then the float ambiguities are used.

Once there is an initial estimate of the ambiguities (either fixed orfloat), an estimate of the baseline between the base station(s) androver(s) can be calculated.

Fixed Solution

Once the double differenced float ambiguities have been resolved intointegers there is a set of double differenced fixed ambiguities. Thefloat baseline vector and its corresponding set of double differencedfloat ambiguities are coupled. Now that these double differenced floatambiguities have been resolved into integers a new fixed baseline vectormay be solved for using the coupled set of double differenced fixedambiguities. The fixed baseline vector is all that is unknown at thispoint so the dimensionality of the problem has been reduced by thenumber of double differenced fixed ambiguities there are. The system ofequations is a smaller version of those used in the float solution dueto there being more known variables and less unknown variables. Thefixed baseline vector may be solved using a variety of methods similarto the float solution, the most popular of which are adjusted leastsquares or Kalman filtering.

INS Verification

Loosely integrated INS can also be used as a secondary validationmeasure. By comparing the change in estimated baselines over time withthe change in position solution calculated by the INS, it will beapparent if the present RTK solution has a large drift. If this is thecase, the double differences will need to be recalculated (likely usingupdated satellite geometry) resulting in new float and fixedambiguities, and a new RTK solution. Any resulting discontinuity in theRTK solution can be mitigated by estimating the position from the INS.

Multibase Verification

Once a fixed solution has been achieved, this result can then be fedback into the verification process in order to further optimize thefixed ambiguities for systems that use more than one base station. Forthis verification step, the fact that the base stations are static andin a known configuration is leveraged to identify which set of fixedambiguities is optimal. Since the base station geometry is known and thebaselines between each base station(s) and rover(s) have been computed,the difference of the baselines between any rover and each base stationshould result in the original base station geometry. Errors in thecurrent fixed ambiguities will result in drift in the RTK solution andlarger errors will result in larger drift. The amount of drift from thecurrent set of ambiguities can easily be estimated by comparing knownbase station geometry to the calculated base station geometry from thecalculated base lines. If another set of validated fixed ambiguitiescreate a smaller error in the geometry, then it is selected as theoptimal set of ambiguities.

In one or more exemplary embodiments, the functions, methods, andprocesses described may be implemented in whole or in part in hardware,software, firmware, or any combination thereof. If implemented insoftware, the functions may be stored on or encoded as one or moreinstructions or code on a computer-readable medium. Computer-readablemedia includes computer storage media. Storage media may be anyavailable media that can be accessed by a computer.

By way of example, and not limitation, such computer-readable media caninclude RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any other medium thatcan be used to carry or store desired program code in the form ofinstructions or data structures and that can be accessed by a computer.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media

The various illustrative functions, modules, and circuits described inconnection with the embodiments disclosed herein with respect topositioning and other signal processing functions, control functions,data communication functions, wireless communications functions, and/orother functions described herein may be implemented or performed in oneor more processing elements or modules with a general purpose processor,a digital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

The presently claimed invention is not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the specification and drawings, wherein reference to an element inthe singular is not intended to mean “one and only one” unlessspecifically so stated, but rather “one or more.” Unless specificallystated otherwise, the term “some” refers to one or more. A phrasereferring to “at least one of” a list of items refers to any combinationof those items, including single members. As an example, “at least oneof: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b andc; and a, b and c.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use embodiments of thepresently claimed invention. Various modifications to these aspects willbe readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other aspects withoutdeparting from the spirit or scope of the disclosure and presentlyclaimed invention. Thus, the invention is not intended to be limited tothe aspects shown herein but is to be accorded the widest scopeconsistent with the appended Claims and their equivalents.

The invention claimed is:
 1. A mobile base station for use in a utilitylocator system to send and receive data to utility locators and utilitylocator transmitters, comprising: a vehicle; a plurality of antennasdisposed on the vehicle, the antennas including a GPS antenna forreceiving GPS signals for determining positions information of thevehicle and a wireless local area network (WLAN) antenna for receivingand sending radio signals; a plurality of receivers disposed on ormounted to the vehicle, the receivers including a GPS receiveroperatively coupled to an output of the GPS antenna for determiningpositioning information of the vehicle based on received GPS signals anda WLAN transceiver coupled to an output of the WLAN antenna forreceiving and sending radio signals including data from and to the oneor more utility locators and the one or more utility locatortransmitters; a processing element disposed on or mounted to on thevehicle, wherein the processing element is communicatively coupled tothe one or more GPS receivers and the WLAN transceivers via acommunication network, to process data received from the one or moreutility locators and one or more utility locator transmitters and storethe data in a non-transitory memory; and a power supply subsystem,disposed on or mounted to the vehicle, for providing electrical powerfor the processing elements and the plurality of receivers; wherein theWLAN transceiver sends positional information associated with thevehicle as determined by the GPS receivers to a one or both of the oneor more utility locators and one or more utility locator transmittersand receives locate data from the one or more utility locators.
 2. Thebase station of claim 1, wherein the vehicle comprises a truck with acap-type structure disposed on a bed of the truck and the antennas aredisposed on an exterior surface of the cap-type structure.
 3. The basestation of claim 2, wherein the plurality of receivers and processingelement are disposed within a space enclosed by the cap-type structure.4. The base station of claim 3, wherein the cap-type structure,receivers, and processing element are mechanically configured to berollably or slidably removable from the truck.
 5. The base station ofclaim 1, further comprising one or more sensors including a multi-axisaccelerometer, a multi-axis compass sensor, a multi-axis gyroscope, abarometer, a light sensor, and a temperature sensor, wherein the one ormore sensors are coupled to the processing element for providing sensoroutput data to the processing element, associating the sensor data withdata provided to the processing element from the one or more utilitylocators, and storing the associated sensor data and data provided tothe processing element in a non-transitory memory on the vehicle.
 6. Thebase station of claim 1, wherein the GPS receiver determines informationfrom GPS signals received at the GPS antenna and sends the determinedinformation to the one or more utility locators.
 7. The base station ofclaim 6, wherein the determined GPS information includes timinginformation.
 8. The base station of claim 6, wherein the determinedinformation includes positional information associated with a positionof the mobile base station.
 9. The base station of claim 6, wherein thebase station provides real time kinetic (RTK) data to the one or moreutility locators for use in correcting GPS positional informationdetermined at the one or more utility locator transmitters.
 10. The basestation of claim 1, wherein the processing element is further configuredto communicate with one or more utility locator transmitters.
 11. Thebase station of claim 10, wherein the GPS receiver determinesinformation from GPS signals received at the GPS antenna and sends thedetermined information to the one or more utility locator transmitters.12. The base station of claim 11, wherein the determined GPS informationincludes timing information.
 13. The base station of claim 11, whereinthe determined information includes positional information associatedwith a position of the mobile base station.
 14. The base station ofclaim 11, wherein the base station provides real time kinetic (RTK) datato the one or more utility locator transmitters for use in correctingGPS positional information determined at the one or more utility locatortransmitters.
 15. A utility locating system, comprising: a mobile basestation including: a vehicle; a plurality of antennas disposed on thevehicle, the antennas including a GPS antenna for receiving GPS signalsfor determining positions information of the vehicle and providing acorresponding GPS antenna output, and a WLAN antenna for receiving WLANradio signals and providing a corresponding WLAN output and forreceiving a WLAN antenna input and sending corresponding WLAN radiosignals from and to one or more utility locators and from and to one ormore utility locator transmitters; a plurality of receivers disposed onor mounted to the vehicle, the receivers including a GPS receiveroperatively coupled to the GPS antenna output, and a WLAN transceiverhaving an output operatively coupled to the WLAN antenna input and aninput operatively coupled to the WLAN antenna output; a processingelement, disposed on or mounted to the vehicle, configured tocommunicate data through the WLAN transceiver and WLAN antenna with onesof the plurality of receivers, one or more utility locators, and one ormore utility locator transmitters; and a power supply subsystem,disposed on or mounted to the vehicle, for providing electrical powerfor the processing elements and the plurality of receivers; one or moreutility locators, separate from the vehicle, including locator WLANtransceivers for communicating with the mobile base station to sendlocate data to and receiver positional information from the mobile basestation; and one or more utility locator transmitters, separate from thevehicle and separate from the one or more utility locators, includingtransmitter WLAN transceivers for communicating with the mobile basestation to send frequency data and/or to receive positional data fromthe mobile base station.